The invention relates generally to fuel cell stacks and modules for power generation, and more particularly, to fuel cell stacks and modules with segregated reactant streams.
Fuel cells, for example solid oxide fuel cells (SOFCs), are energy conversion devices that produce electricity by electrochemically combining a fuel and an oxidant across an ionic conducting layer. The fuel cell operating temperatures depend on the material forming the ionic conducting layer. Desirably, power generation systems incorporating high-temperature fuel cells have the potential for higher efficiencies and power outputs. Exemplary high-temperature fuel cells have operating temperatures above about 600° C., and exemplary SOFCs operate in a range of about 800 to about 1000 degrees Celsius.
A typical fuel cell operates at a potential of less than about one (1) Volt. To achieve sufficient voltages for power generation applications, a number of individual fuel cells are integrated into a larger component. Separation of the oxidant and fuel streams is desirable for multistaging and the use of reactant products by other devices in a power generation system. For lower temperature fuel cells, for example having an operating temperature of less that about 200° C., a large number of elastomer seals in compression may used to separate the two reactants. Elastomer seals cannot withstand the operating temperatures of high-temperature fuel cells, and consequently other materials, such as glass ceramics, must be used to form the seals. However, seal performance remains problematic for high temperature fuel cells, in particular for designs requiring sealing of cell edges or corners or for other joint designs that require maintaining a gap of a certain size during thermal expansion and contraction cycles.
It would therefore be desirable to design a fuel cell stack that maintains separation of the reactant streams, using a reduced number of seals. It would further be desirable to incorporate the fuel cell stack into a fuel cell module having redundant current paths.